Evaluation of Concrete Chimneys Designed According to ACI 307 Standard

This paper evaluates chimneys designed for earthquake and wind forces per ACI 307-98 and the revised earthquake loading provisions of the ACI 307-08 standard. ACI 307 standard presents a comprehensive set of guidelines for analysis, design and detailing of reinforced concrete chimneys in the United States. Three chimneys of various heights and diameters with multiple openings of various sizes designed per ACI 307-98 are analyzed using 3D linear finite element analysis program GTSTRUDL/ANSYS to check adequacy of the standard. It is shown that chimneys designed per ACI 307-98 standard would invariably result in either insufficient strength and/or detailing around openings which can only be captured by a 3D finite element analysis approach [not by beam element analysis combined with sectional design approach proposed in the ACI 307 standard.] This overstress and lack of confinement detailing around openings will likely result in progressive degradation of structural performance of the chimneys as it responds to the multiple and reverse cycles of wind or earthquake forces. It is recommended that a 3D FEM analysis should be performed, in the most critical direction of the chimneys with openings, in order to estimate the possible stress overload and need for confinement of critical regions of RC chimneys.